Showing papers in "Parasitology in 1958"

Observations on the development of Toxocara canis (Werner, 1782) in the dog.

Abstract: 1. Evidence from previous literature shows that puppies are commonly infected with larvae of Toxocara canis at birth and that prenatal infection can be produced by feeding embryonated eggs to pregnant bitches.2. Observations on fifty-eight dogs in Brisbane showed that all of twenty-nine puppies 1–6 months old were infected, while only three out of twenty-nine dogs over 6 months old were infected.3. In naturally infected puppies, 1–3 weeks old, it was found that at birth third-stage larvae were present in the lungs. Third-stage larvae continued to appear in the lungs for the first week of life; their length was 0·6–1·3 mm.4. Third-stage larvae were found in the stomach on the day after birth; at 3 days after birth fourth-stage larvae were found in the intestine.5. It appeared likely that the second moult occurs in puppies before birth, and that the third moult takes place at a length of 1·0–1·3 mm. in the lungs and stomach within the first week of life.6. By the beginning of the second week, fourth-stage larvae were fully grown and had commenced the fourth moult at a length of 5–7 mm.7. Throughout the second and third weeks, adults grew rapidly, reaching a length of about 67 mm. by the end of the third week, but no eggs had appeared in the faeces at this time.8. Experimental infection of mice with eggs showed that the larvae were distributed to the somatic tissues, few reaching the alimentary tract. The larvae did not progress beyond the second stage in the tissues of mice.9. Experimental infection of dogs with eggs showed that in dogs over 5 weeks old the larvae were distributed to the somatic tissues and did not reach the alimentary tract. The larvae did not progress beyond the second stage, though some of them showed signs of commencing the second moult. In contrast, 1 to 3-week-old puppies infected in the same way were found to harbour larvae in the alimentary tract. Though some of these larvae were probably derived from a naturally acquired prenatal infection, it was evident from the progress of development that the experimental infection resulted in the presence of second-stage larvae in the liver and lungs and that these larvae underwent the second moult, commenced development as third-stage larvae in the lungs, migrated into the stomach and developed to the adult stage in the intestine.10. Experimental infection of dogs and foxes with mice harbouring second-stage larvae in the tissues showed that, in some instances, development of larvae proceeded in the alimentary tract. No evidence of somatic migration was found in dogs infected in this way, but in foxes second-stage larvae were found in the lungs.11. The structure and development of the second, third and fourth stage is described in detail and found to resemble closely the development of T. cati larvae (Sprent, 1956). Second-stage larvae from dog tissues had a length of 0·34–0·44 mm. and the second moult occurred at a length of 0·37–0·44 mm. Third-stage larvae varied in length from 0·46 to 1·36 mm., and the third moult occurred at a length of 0·98–1·3 mm. Fourth-stage larvae measured 1·2–6·3 mm., though moulting fourth-stage larvae were observed up to a length of 7·4 mm. Sexual differentiation occurred during the fourth stage and was evident at a length of about 1·5 mm.12. The migratory behaviour of the larvae of T. canis and T. cati is compared and discussed in relation to their wide range of hosts. It is concluded that differences in migratory behaviour are adaptations to prevailing modes of nutrition and it is suggested that the somatic migration occurring in dogs is an adaptation to the non-predatory habits of this particular host.

Studies on the morphology, biology and development of a strigeid cercaria (Cercaria X Baylis 1930).

Abstract: 1. Cercaria X (Baylis & Taylor, 1930) and its sporocyst have been redescribed with some additions to the original descriptions.2. The details of the development of the cercaria into a metacercaria of the diplostomulum type have been obtained and the anatomy of the mature metacercaria is described in detail for the first time. It is proposed to name the metacercaria Diplostomulum X. Development of the cercaria into a metacercaria takes from 40 to 90 days and the metacercariae have been shown to survive for a period of 544 days after the time of infection. This development has been obtained in the lenses of rats, frogs and a wide variety of fish. Development is not completed in any other region of the host's body.3.The effect of the sporocyst, migration of the cercariae, and the metacercaria on the appropriate host tissues has been considered. All these stages produce extensive changes in the host tissues.4. Histochemical tests have shown the presence of alkaline phosphatase activity in the cuticle of the sporocyst. The glycogen storage regions of the cercaria are described and it has been demonstrated that the caudal bodies in the tail-stem contain large amounts of glycogen which are utilized during the free-swimming period.5. Attempts at the completion of the life cycle were unsuccessful.

Cytological and histochemical criteria for evaluating development of trematodes and pseudophyllidean cestodes in vivo and in vitro.

Abstract: 1. Maturation of the plerocercoid of the pseudophyllidean cestode Diphyllobothrium sp. and the metacercaria of the strigeid trematode Diplostomum phoxini follow a similar pattern, which may be divided into the following phases: (1) cell multiplication; (2) segmentation or body shaping; (3) organogeny; (4) early gametogeny; (5) late gametogeny; (6) egg-shell formation and vitellogenesis; (7) oviposition.2. Cytological or histochemical criteria have been developed by means of which each developmental phase may be recognized. Development in vitro may be considered comparable with that occurring in vivo if the same phases are completed with the same incubation time and without the appearance of cytological abnormalities.3. The cell multiplication phase is characterized by high mitotic activity. This activity in vitro can be evaluated by incubating larvae after 24 hr. culture for a standard time (5 hr. Diphyllobothrium; 4 hr. Diplostomum) in 10−4 colchicine and comparing the number of mitoses seen in a defined area of an aceto-orcein squash with those found in tissue matured in vivo for the same period. Use of this criterion enables the growth-producing properties of a medium to be assessed after 24 hr. culture.4. Phases 2–4 are characterized by the appearance of the tubular genitalia, the rudiments of which are readily recognized in aceto-orcein squashes or whole mount preparations.5. The presence of spermatids and mature spermatozoa (phases 4–5) may be detected in aceto-orcein squashes or in fresh tissue teases. The quantity and activity of spermatozoa also serve as important criteria.6. Recognition of phase 6, egg-shell formation, is carried out by means of diazo reagents which give orange or orange-red reactions with the phenolic egg-shell precursors in the vitellaria, as seen in whole mount preparations. Abnormal egg-shell development is reflected in the failure of vitellaria to give a normal diazo reaction.7. The appearance of eggs which are macroscopically normal constitutes the final maturation phase. Early detection of eggs (especially abnormal ones) is facilitated by the use of the diazo reaction or the catechol test for polyphenol oxidase.8. Embryonation and hatching of eggs to produce morphologically normal infective coracidia or miracidia serve as a final criteria.9. Criteria for the maintenance of the adult condition are also considered.

Nematode parasite populations in sheep on lowland farms. V. Further observations on the post-parturient rise and a discussion of its significance.

Abstract: In a previous paper (Crofton, 1954) it was shown that the rise in egg counts occurring in ewe flocks in spring was related to the time of lambing. It was further shown that the rise in individuals occurred about 6 weeks after parturition and was normally of short duration. While the mean time of increased egg count for each individual was about 2 weeks, the increased egg count in the flock was spread over a period equivalent to the length of the lambing period. It is clear that the apparent rise in the flock as a whole will be greatest when all the flock lambs within a short period. With greater scatter of times of parturition the flock rise will be smaller but will extend over a greater period. This association of rise in egg count with time of parturition is obviously one of considerable selective advantage, in so far as an increase in infective stages will occur at a time when the susceptible lambs have a reduced milk intake and an increased grass intake. The synchronization of availability of infective stages and the occurrence of susceptible individuals is further emphasized by the relation of the period of increase to the time of birth of the lambs, the duration of the period of increase in the flock being directly proportional to the duration of the lambing period. This type of ‘escapement’ control is seen in so many other host-parasite relationships that it makes considerable appeal on general grounds. Other workers, Morgan, Parnell & Rayski (1951), have, however, related the rise in egg counts to climatological factors, but climatic control would not give the close synchronization described above.

Electron microscopic study of Trypanosoma cruzi in thin sections of infected tissue cultures and of blood-agar forms.

Abstract: Thin sections of Trypanosoma cruzi in tissue cultures and from blood agar medium have been examined with the electron microscope.In the leishmania and crithidia forms of the parasite a neat separation of kinetonucleus and blepharoplast has been obtained and these structures are described. The blepharoplast is the row of basal corpuscles which give origin to the axial fibres of the flagellum.Division of the parasite seems to begin in the basal corpuscles; it is followed by binary division of the kinetonucleus and only later by fission of nucleus and cytoplasm.During the development of the leishmania into the crithidia form, the kinetonucleus and basal bodies are dislocated towards the posterior half of the trypanosome. The migration of these two structures and the consequent lengthening of the flagellum causes the surface membrane of the flagellum to be pushed inwards to form a deep invagination, so that the flagellum comes to the surface of the body and is separated from it along its whole length by its own sheath.In the adult form of the parasite a great vacuole is formed near the posterior tip of the trypanosome. It has no definite structure in the electron microscope, is transparent and seems to be filled with a liquid content. The basal corpuscles are situated in this region near the wall of the vacuole. The typical structure of the kinetonucleus could not be identified with certainty in these forms; it seems to be altered by the formation of the vacuole.The vacuole is crossed by a fibre system which comes from the body of the trypanosome and is often dislodged by the size of the vacuole. This fibre system ends in a sharply pointed process of varying length.The cost of reproduction of figures was defrayed by the Instituto de Biofisica da Universidade do Brasil.

Nematode parasite populations in sheep on lowland farms. VI. Sheep behaviour and nematode infections.

Abstract: It is usual, when considering the trichostrongyle infections of sheep, to refer to parasitic stages in the host and free-living stages on pasture as two separate entities with ecological, structural and physiological differences emphasized by their temporal relationship. They are, however, interlinked phases in a continuous exchange process in which the host acts as a vehicle. The role of the host as a mediator in this exchange has received little attention until recently and has been mainly restricted to a more dynamic approach to problems of immunity. The behaviour of the host, as well as that of the parasite, is obviously of great importance, but there has been little work on the behaviour of sheep in relation to patterns of helminth infections, although Taylor (1954) discussed the problem in general terms.

The epidemiology of the infestation of the honeybee, Apis mellifera L., by the mite Acarapis woodi Rennie and the mortality of infested bees.

Abstract: The proportion of young honeybees which became infested with Acarapis woodi Rennie rose with an increased degree of infestation of the older bees and increased temperatures. But the most important influence controlling infestation seems to be the frequency with which young and old bees come into contact; this is probably determined by the foraging activity of the bees and the ratio of young bees to old bees; the percentage of infested bees in colonies diminished rapidly during nectar-flows and rose in periods of little nectar-flow.The mortality of infested bees was only slightly greater than that of non-infested bees and became evident only after the bees had been in prolonged unfavourable circumstances. There were no obvious signs of disease in heavily infested colonies in summer. Colonies with more than about 30 or 40 % of infested bees seemed more likely to die in winter than non-infested colonies, but few colonies became so heavily infested even after a very poor season.

Studies on Crepidostomum metoecus (Braun) and C. farionis (Müller), parasitic in Salmo trutta L. and S. salar L. in Britain.

Abstract: 1. Crepidostomum farionis (Muller, 1784) and C. metoecus (Braun, 1900) were found to occur together in the same host fish, Salmo trutta L., S. salar L. and Anguilla anguilla (L.) in mid-Wales. It is believed that the latter species constituted an accidental host.2. C. metoecus is recorded in Britain for the first time.3. There was some evidence of a habitat isolation in individual fish as C. metoecus occurred predominantly within the pyloric caeca, while C. farionis usually occupied a more posterior station in the intestine.4. A detailed description is given of G. metoecus and the salient features of this species are compared with those of C. farionis.5. The two species of Crepidostomum commonly occurred in large numbers in their fish hosts, individual fish harbouring up to 157 worms. No lesions attributable to Crepidostomum were, however, detected and there was no evidence of pathogenicity.6. It would appear that the eel is physiologically immune to both species of Crepidostomum and that the salmon parr is partially resistant.7. The degree of infestation of trout and parr with both the Crepidostomum species is at a maximum during the winter months and at a minimum in the summer months. This seasonal variation can be attributed to a periodicity in the swarming of the cercariae.8. There is no evidence of age resistance or acquired immunity of the trout to infestation by Crepidostomum species.

Life history and pathogenicity of Eimeria adenoeides Moore & Brown, 1951, in the turkey poult.

Abstract: The life cycle and pathogenicity of a strain of Eimeria isolated in Great Britain from turkey poults by single cell inoculation are described and, using the criteria laid down by Tyzzer, the species is identified as E. adenoeides.The life cycle is of the same general pattern as in other Eimeria species, consisting of two asexual and one sexual generations.The organism is highly pathogenic for young poults, a dose of 200,000 oocysts producing 100 % mortality in 3-week-old birds and smaller doses causing reduced weight gain. Birds 11 weeks old resisted a dose of 3 million oocysts.The gross and microscopic pathology of the infection is described. No changes were found in the blood picture.

A study of the early stages of infection with the Tipula iridescent virus.

Abstract: Ultra-thin sections and electron microscopy have been used in a study of the empty membranes which occur in the fatbody cells of the larva of T. paludosa infected with the Tipula Iridescent Virus (TIV). It has been observed that these empty membranes are most numerous in the early stages of infection. Later an apparent ‘primary body’, which may be threadlike in its initial stages, develops in the centre of the membrane. This primary body seems to increase in size until the membrane is filled, and the various steps in this process can easily be seen. It is suggested that the formation of the empty membranes and the apparent gradual development of their contents are the means by which the virus multiplies. The remarkable resemblance between the empty virus membranes and the endoplasmic reticulum is pointed out.

Experimental Eimeria mitis infections in chickens.

Abstract: 1. Methods are described for the isolation and maintenance of a pure strain of Eimeria mitis.2. The prepatent period of the infection in chicks was 101 hr. The mean dimensions of the oocysts were 15·38 × 13·83μ, and sporulation occurred after 48 hr. at 60° F. (15·5° C.). The production of oocysts following infection with known numbers of oocysts is recorded.3. When 500,000 or more oocysts of E. mitis were given to chicks aged 6, 17 or 26 days the growth rate of the birds was markedly reduced. Young chicks were most susceptible and a few deaths occurred when 6-day-old chicks received 2·5 million oocysts. E. mitis is unlikely to be of pathological importance under normal conditions of good husbandry practice.4. Pathological lesions due to this species of Eimeria were not found in sections of intestinal tissues.5. Developmental stages of this parasite were found throughout the whole of the small intestine.6. The growth-retarding effects and oocyst production by E. mitis were controlled when 0·2% sodium sulphadimidine was given in the drinking water.

A revision of the nematode genus Meteterakis Karve, 1930.

Abstract: 1. The genus Meteterakis is reconstituted with eight species: M. govindi, M. louisi, M. baylisi, M. longispiculata, M. cophotis, M. japonica, M. mabuyi and M. triaculeata.2. M. cophotis, M. japonica and M. longispiculata were previously placed in the genus Spinicauda.3. M. mabuyi was previously in the genus Africana.4. M. triaculeata was previously in the genus Ganguleterakis.5. M. baylisi and M. louisi are new species.6. Spinicauda bufonis and, probably, Africana varani are considered synonyms of M. govindi.7. Africana howardi is considered a synonym of M. japonica.8. A list of the remaining species in the genera Africana and Spinicauda is given.

Further observations on the structure of nematode cuticle

Abstract: 1. An examination of the cuticle of Oxyuris equi has revealed the presence of previously unidentified structures. The layers of the cuticle of this nematode have been renamed.2. The cuticle of Strongylus equinus has been examined in a similar fashion and, whilst the basic nomenclature of the various layers has been retained, previous descriptions of the individual layers have been modified and extended.3. Further evidence is put forward in favour of the presence of pore canals in the cuticle of Ascaris lumbricoides.

Structure, hatching and size variation of the spores in a species of Nosema (Microsporidia) found in Hyalophora cecropia (Lepidoptera)

Abstract: 1. A brief outline of the life cycle of a species of Nosema parasitic in Saturniid moths is given. It is of the normal type.2. The structure of the spore is described, and from electron microscopy evidence is presented which supports the theory that the sporoplasm is injected into the host's tissue.3. The volume of the spore is affected by the ambient medium, by the pretreatments of fixation and of desiccation, by the site of development within the host and by the age of the host.4. These results have been discussed with reference to the use of spore size as a diagnostic character in the classification of the Microsporidia. It is concluded that spore size is not a reliable character for taxonomic purposes.

A comparison of the structure of the scolex of Bothriocephalus scorpii (Müller 1776) and Clestobothrium crassiceps (Rud 1819) and the mode of attachment of the scolex to the intestine of the host.

Abstract: 1. Two Pseudophyllidea, Bothriocephalus scorpii (Muller) and Clestobothrium crassiceps (Rud.), have been obtained from Scophthalmus maximus (L.) and Merluccius merluccius (L.) respectively, from fishing grounds to the west of the British Isles.2. The musculature of the scolex in both has been compared relative to the form and mode of function of that organ. All the major groups of muscles are present in both, but their arrangement is modified in C. crassiceps, due to the presence of hemispherical bothria, instead of open grooves, and a sphincter muscle around the bothrial opening.3. The mode of attachment is discussed briefly in C. crassiceps, and in more detail in B. scorpii, where the structure of the scolex was found to be admirably suited to the form of the host's mucosa. The effect on the mucosa is slight, due to the absence of very powerful muscles and of other specialized adhesive structures.4. The nervous system of the scolex in both species has been compared, and a fundamental similarity has been found. Modifications in C. crassiceps are associated with shortening of the scolex and the difference in form of the bothria.5. The excretory system shows the same correlation with the form of the scolex.

Digestion in Leidynema appendiculata (Leidy, 1850), a nematode parasitic in cockroaches.

Abstract: 1. A study of the digestive enzymes present in the nematode Leidynema appendiculata, parasitic in the cockroach, gave the following results.2. An amylase with optimum activity at pH 4·5, is present. Sodium chloride increases activity by 29 % at this pH.3. A maltase, with maximum activity at pH 5·0–6·0, is present. It is completely inhibited by 15 % glycerin.4. Lactase and invertase were not detected.5. A protease, capable of clotting calcified milk, and of splitting gelatin and edestin, with maximum activity at pH 6·0, is present. KCN does not increase activity.6. Peptidases splitting glycyl-glycine, dl-leucyl-glycine and dl-leucyl-glycyl-glycine, and a prolidase splitting glycyl-l-proline are present.7. A lipase hydrolysing glycerol tributyrate, with maximum activity at pH 7·0 is present. Hydrolysis of olive oil and ethyl butyrate was not detected.8. It is concluded that these enzymes are quite distinct from those of the host and that digestion probably takes place over the range of pH 5·5–6·0.

The effects of trematode metacercariae (Brachylaemidae) on the slugs Milax sowerbii ferussac and Agriolimax reticulatus Müller.

Abstract: 1. Infestation of the kidney of M. sowerbii and A. reticulatus by unencysted brachylaemid metacercariae led to a widespread necrosis of the organ. The necrotic debris was ingested into the gut crura of the parasites. 2. M. sowerbii is considered to be a natural intermediate host of the parasite and A. reticulatus to be an unnatural host, because in A. reticulatus parasitization led to a host mortality closely related to the degree of infestation, whereas M. sowerbii withstood the damaging effects of parasitization until the parasites reached maturity. 3. In A. reticulatus the rate of ingestion of food and the rate of egg production were reduced during parasitization. 4. No further effects were observed in either host species. 5. The possibilities and difficulties of using unencysted metacercariae to control pests are discussed.

The sheep ked, Melophagus ovinus L. I. Dissemination potential.

Abstract: Components of the intricate ked-sheep pattern, of significance in dissemination of the ked, are defined. It was found that the dissemination potential (percentage of population on the fleece surface) on one sheep was constantly greater than on a second. Bright sunshine caused an increase in the dissemination potential, particularly on the first sheep. It was concluded that the stimulating factor was a rise in the fleece temperature in regions directly exposed to the rays of the sun.The factor or factors causing differences in dissemination potential arose from similar degrees of temperature change being superimposed on inherently different fleeces. The sexes behaved similarly on both sheep.Keds were able to transfer readily between the two sheep. However, when they were concentrated on the sheep with a high dissemination potential, the population of the two-sheep system declined rapidly; when they were placed on the sheep with a low dissemination potential, the population of the two-sheep system increased. Approximately half of the keds leaving the sheep with a high dissemination potential did not reach a second host. It thus acted as a disinfecting agent.Bird and host predation were discounted as factors in causing ked population change.

The physiology of digestion in the larvae of the horse bot-fly, Gasterophilus intestinalis (De Geer).

Abstract: 1. Evidence is produced to show that the larvae of Gasterophilus intestinalis are occasional blood feeders but normally feed on tissue exudate.2. The demonstration, by Roy (1937), of the following enzymes has been confirmed and curves of their activity at different hydrogen-ion concentrations have been constructed: mid-gut amylase, proteinase and lipase.3. The following enzymes have been demonstrated and curves of their activity at different hydrogen-ion concentrations have been obtained: maltase, invertase, polypeptidase and di-peptidase of the mid-gut and amylase, maltase and invertase of the salivary glands.4. The haemolymph was shown to contain a lipase as well as an amylase and an anticoagulin.

The gametogenesis of the digenetic trematode Sphaerostoma bramae (Müller) Lühe.

Abstract: The stages of spermatogenesis and the structure of the primary oocyte of Sphaerostoma bramae were studied in material fixed in Bouin and Flemming's fluid and in preparations treated according to the Kolatchev and the Feulgen techniques. Chromosome counts of primary and secondary spermatocytes indicate that the diploid number is twenty-four. The stages of spermatogenesis, in general, conform to the usual pattern of this process in digenetic trematodes. The spermatogonia, spermatocytes and early spermatids are not connected together by central strands, nor by a central disk, as is claimed for some other species. A study of sections stained in haematoxylin and of Feulgen preparations showed that the spermatozoon is composed of an elongate nucleus and a tail. It was not possible, with the methods employed during the present investigation, to determine the fine structure of the tail. The primary ovarian oocytes are in the interphase or in early prophase of the first maturation division. There is evidence that material is extruded from the nucleus to the cytoplasm. The Golgi elements of the male germ-cells are revealed in Kolatchev preparations as short rods and filaments. The Golgi elements of the spermatid are eliminated in the residual cytoplasm. Mitochondria, in the form of granular bodies and short rods, were visible in spermatogonia, spermatocytes and spermatids. Those of the spermatid remain in the residual cytoplasm. Short, rod-like Golgi bodies are present in the primary oocytes. In the young cells they form a compact mass situated close to or in contact with the nuclear membrane. Later, the elements spread out through the cell. Granular and rod-shaped mitochondria are concentrated in a single mass at one pole of the nucleus or in two masses at opposite sides of the nucleus. A few mitochondria are scattered through the cytoplasm.

The vector of Hepatozoon sciuri.

Abstract: A description is given of the stages of sporogony of Hepatozoon sciuri, which have been found in three wild fleas (Orchopeas wickhami) out of a total of nearly sixty specimens collected from squirrels in England. Although an attempt to infect the fleas in the laboratory, by feeding them on infected squirrels, failed, the above findings indicate that these fleas may act as vectors of the squirrel parasite.We wish to record our thanks to Professor P. C. C. Garnham for his kind interest and constructive suggestions regarding this work. We are specially indebted to Mrs M. Vizoso and to Dr J. F. D. Frazer for sending us fleas and squirrels from time to time. Our thanks are due to the authorities of the British Museum of Natural History for the identification of the flea.

On the morphology of the male, female and fourth-stage larva (female) of Hammerschmidtiella diesingi (Hammerschmidt), a nematode parasitic in cockroaches.

Abstract: The male, female and fourth-stage larva (female) of Hammerschmidtiella diesingi are described. Characters are given by which this species can be identified from the female fourth-stage larva.A constriction and ring of clear cells separate the intestine of the male and of the female fourth-stage larva into two parts, and descriptions of the structure and mode of action of this ‘sphincter’ are given.This work was carried out during the tenure of a Research Studentship awarded by the Department of Scientific and Industrial Research.

The bird fleas of Fair Isle.

Abstract: Approximately 5000 birds (78 species) were trapped on Fair Isle and examined for fleas. Six species of flea were recorded: D. g. gallinulae (430 records), C. gallinae (205 records), C. borealis (126 records), C. garei (4 records), C. fringillae and C. vagabundus (1 record each).The infestation rate among spring-passage migrants was 52·2% and among autumn-passage migrants only 2·7%. Spring migrants released and retrapped after ‘de-fleaing’ in the Fair Isle apparatus showed a 55% re-infestation rate. On spring migrants D. g. gallinulae was the dominant flea, but on autumn migrants C. gallinae was dominant. The most heavily infested group of birds were the Turdidae (61% spring, 3% autumn infestation rate) and Sylviidae (53% spring, 1% autumn infestation rate).A number of double and triple infestations with 2 or 3 species of flea is recorded. Double infestations involving D. g. gallinulae and C. borealis occur more frequently than would be expected for purely chance associations. More male birds (90) than female birds (70) were infested.The sex ratio of the fleas (on the bodies of birds) was: D. g. gallinulae 294 males, 325 females; C. gallinae 115 males, 214 females; C. borealis 77 males, 77 females. On the spring migrants there was an excess of male D. g. gallinulae and on the autumn migrants an excess of females.On the resident birds there was definite evidence of host preference. The starling was the chief host of C. gallinae, the pipits of D. g. gallinulae and the wheatear of C. borealis. The re-infestation rate of ‘de-fleaed’ retraps showed a higher rate than original trappings in all cases, but the lack of D. g. gallinulae on retrapped starlings suggested some host selection on the part of the flea.The proportions of the three principal species of flea found in (i) the nest of the wheatear, and (ii) on the body of the bird were strikingly different.

A new schizogregarine, Mattesia orchopiae n. sp., in a flea of squirrels in England.

Abstract: A new schizogregarine Mattesia orchopiae , n.sp., parasitic in the flea Orchopeas wickhami , is described. The schizogony takes place in the fat-cells, while the gametogony and the sporogony occur in the Malpighian tubules. The micronuclear schizonts measured 13·7 × 11 μ. The trophozoites of the second schizogony measured 14·2 × 3·5 μ. The spores measured 10·5 × 7 μ. After staining with toluidene blue metachromatic granules were found in the cytoplasm of the macronuclear schizonts and in the merozoites and the trophozoites resulting therefrom. Some of this metachromatic material could be removed by digestion with ribonuclease, while the rest of it persisted. Material stained with alcian blue was detected in the cytoplasm of the macronuclear schizonts. I wish to thank Professor P. C. C. Garnham for encouragement and advice received during the conduct of this investigation, Mrs M. Vizoso and Miss K. Meedeniya for the supply of the fleas, the authorities of the British Museum for the identification of the fleas, and Sir W. P. MacArthur for his advice regarding the problem of nomenclature.